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source: branches/f4grobner/term.lisp@ 3263

Last change on this file since 3263 was 3219, checked in by Marek Rychlik, 9 years ago

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1;;; -*- Mode: Lisp -*-
2;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
3;;;
4;;; Copyright (C) 1999, 2002, 2009, 2015 Marek Rychlik <rychlik@u.arizona.edu>
5;;;
6;;; This program is free software; you can redistribute it and/or modify
7;;; it under the terms of the GNU General Public License as published by
8;;; the Free Software Foundation; either version 2 of the License, or
9;;; (at your option) any later version.
10;;;
11;;; This program is distributed in the hope that it will be useful,
12;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
13;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14;;; GNU General Public License for more details.
15;;;
16;;; You should have received a copy of the GNU General Public License
17;;; along with this program; if not, write to the Free Software
18;;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19;;;
20;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
21
22(defpackage "TERM"
23 (:use :cl :monom :ring)
24 (:export "TERM")
25 (:documentation "This package implements class TERM. A term is a
26product of a scalar and powers of some variables, such as
275*X^2*Y^3. The part of the term without the coefficient is a monomial
28X^2*Y^3, which is represented by class MONOM, provided by the :MONOM
29package. In this implementation, a TERM specializes MONOL. Also, a
30monomial can be considered a TERM whose coefficient is the unit
31element (1) of the underlying ring. The generic method CHANGE-CLASS
32can be used to convert between a MONOM and a TERM, observing this
33convention."))
34
35(in-package :term)
36
37(proclaim '(optimize (speed 3) (space 0) (safety 0) (debug 0)))
38
39(defclass term (monom scalar)
40 ()
41 (:default-initargs :dimension nil :exponents nil :coeff nil)
42 (:documentation "Implements a term, i.e. a product of a scalar
43and powers of some variables, such as 5*X^2*Y^3."))
44
45(defmethod print-object ((self term) stream)
46 (print-unreadable-object (self stream :type t :identity t)
47 (with-accessors ((dimension monom-dimension)
48 (exponents monom-exponents)
49 (coeff scalar-coeff))
50 self
51 (format stream "DIMENSION=~A EXPONENTS=~A COEFF=~A"
52 dimension exponents coeff))))
53
54
55(defmethod r-equalp ((term1 term) (term2 term))
56 (and (r-equalp (scalar-coeff term1) (scalar-coeff term2))
57 (= (monom-dimension term1) (monom-dimension term2))
58 (equalp (monom-exponents term1) (monom-exponents term2))))
59
60(defmethod update-instance-for-different-class :after ((old monom) (new scalar) &key)
61 (setf (scalar-coeff new) 1))
62
63(defmethod multiply-by :before ((self term) (other term))
64 "Destructively multiply terms SELF and OTHER and store the result into SELF.
65It returns SELF."
66 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other))))
67
68(defmethod left-tensor-product-by ((self term) (other term))
69 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other)))
70 (call-next-method))
71
72(defmethod right-tensor-product-by ((self term) (other term))
73 (setf (scalar-coeff self) (multiply-by (scalar-coeff self) (scalar-coeff other)))
74 (call-next-method))
75
76(defmethod left-tensor-product-by ((self term) (other monom))
77 (call-next-method))
78
79(defmethod right-tensor-product-by ((self term) (other monom))
80 (call-next-method))
81
82(defmethod divide-by ((self term) (other term))
83 "Destructively divide term SELF by OTHER and store the result into SELF.
84It returns SELF."
85 (setf (scalar-coeff self) (divide-by (scalar-coeff self) (scalar-coeff other)))
86 (call-next-method))
87
88(defmethod unary-minus ((self term))
89 (setf (scalar-coeff self) (unary-minus (scalar-coeff self)))
90 self)
91
92(defmethod r* ((term1 term) (term2 term))
93 "Non-destructively multiply TERM1 by TERM2."
94 (multiply-by (copy-instance term1) (copy-instance term2)))
95
96(defmethod r-zerop ((self term))
97 (r-zerop (scalar-coeff self)))
98
99#|
100
101(defun term->cons (term)
102 "A human-readable representation of a term as a cons (MONOM . COEFF)."
103 (declare (type term term))
104 (cons (monom->list (term-monom term)) (scalar-coeff term)))
105
106|#
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